WorleyParsonsWorleyParsons Global NuclearGlobal Nuclear

Regional Workshop on Ad anced Le el 2 Probabilistic SafetRegional Workshop on Advanced Level 2 Probabilistic Safety Analysis (PSA Level 2)

Bulgaria Sofia 15 19 July 2013Bulgaria, Sofia, 15-19 July, 2013

Alexander Wolski, Director Strategic Projects

Industry Leadery

2 19-Sep-13

Global ReachGlobal Reach

A combination of extensive global resources, world recognized technicalA combination of extensive global resources, world recognized technical expertise and deep local knowledge

40,800 personnel |163 offices | 41 countries

Stress Test ReportsW l P A l i d R ltReviewed and analyzed all EU Progress and Final Stress Tests reports + id tifi d l t d th d l t i l di IAEA id

WorleyParsons Analysis and Results

identified related methodology reports, including IAEA guidance• Developed an activity & task-level work breakdown structure (WBS) for performing

stress testsE t t d ll id tifi d b t i t ( h th l d f d d• Extracted all identified robustness improvements (whether already performed, under implementation, planned or proposed) and developed categorized Improvements Database

Improvements DatabaseG i C t i ti d C R f iGrouping, Categorization and Cross-Referencing

SEISMIC

►> 1500 d t i t GeneralFLOODINGGeneralFlooding protection engineering features/structures, e.g. dykesEXTREME WEATHER CONDITIONSELECTRICAL SYSTEMS

►> 1500 raw data improvements►Condensed to 209 across 72 plants

Almaraz ■■

Asco ■■

Emergency diesel generator (EDG) (Primary)Mobile diesel generator (MDG)…BatteriesHEAT REMOVAL SYSTEMSGeneral

Belene ■■

Borssele ■

Safety injection systems…Spent fuel poolMobile pumpsACCIDENT MANAGEMENTGeneral

…

…

PWR / VVER ■BWR �

GeneralStaffingProcedures (Development & updating)…Hydrogen analysis and mitigationEx-vessel coolingOTHER / GENERAL

Vandellos II ■

Zaporizhzhya ■■■■■■

PHWR ♦UNGG / AGR / Magnox ○

RBMK ‡

OTHER / GENERAL…

RBMK ‡

On-Going EffortsP d t / S l ti D l t

Hardened Vent Design• Finalized for Excelon & PPL plants

Product / Solution Development

• Finalized for Excelon & PPL plants• Dry filter system developed

Passive Spent Fuel Cooling• VVER Pools and internals modeled• Residual Heat calculations finished• Mitigation strategies defined, engineered

solutions under developmentHydrogen mitigationHydrogen mitigation• WP MELCOR containment model for VVER-

1000/1200• Cooperation with Bulgarian Academy of Science

Alternative Battery Systems• Identified high-capacity FePO4-battery systems• Commercial dedication on-going

Alternative EPS using GTG0.4

0.45CVH-X.4.14CVH-X.4.15CVH-X.4.22 Alternative EPS using GTG

• Relationship with Kawasaki and Siemens• Joint definition of design & testing requirements

Steam-driven Aux F/W pumps0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

-2000 0 2000 4000 6000 8000 10000 12000 Steam driven Aux F/W pumps• Transfer US concept to VVER

time, sec

IAEA policy on PSAIAEA policy on PSA

PSA is recognized to provide important safety insights in addition to those provided by deterministic safety analysis.

IAEA pays a lot of attention and provides broad spectrum of support in PSA development and assessments. S p

• Level 1 PSAs have now been carried out for almost all NPP worldwide. • Level 2 PSAs have been, or are being, carried out for most NPP , g,

worldwide.• Level 3 PSAs have been carried out for some NPP in some States.

PSA level 2PSA level 2

Level 2 PSA deals with assessment of the last physical barrier in DID concept –Containment.Containment.

In Level 2 PSA, the chronological progression of core damage sequences identified in Level 1 PSA is evaluated, including a quantitative assessment of , g qphenomena arising from severe core damage to reactor fuel.

Level 2 PSA identifies ways in which associated releases of radioactive material from fuel can result in releases to the environment.

Containment event tree analysis models the accident progression and identifiesthe accident sequences that could challenge the containment and release radioactive material to the environment.

Codes for SA Analysis

Several thermal hydraulic codes are used for assessment and evaluation of Severe Accidents.

MAAP (EPRI) d MELCOR (S di NL f NRC) i USAMAAP (EPRI) and MELCOR (Sandia NL for NRC) in USAASTEC (IRSN and GSR) in Germany and France

Country specific codes for other countries Canada Japan RussiaCountry specific codes for other countries – Canada, Japan, Russia

MELCOR is the most used for SA evaluation for VVER reactors outside Russia.

MELCOR is extensively validated against experimental data. Adopted by aworldwide group of users in regulatory, research and utility organizations.

Modularly structured in interchangeable code packages with well-definedinterfaces.

Containment Filtered VentingR ti l

S id t lt i d t t

Rationale

Severe accidents can result in pressure and temperature increase which may lead to containment failure and uncontrolled release of radioactive products to the penvironmentStress Test Results - “Containment venting must be

id d i th filt d i d f id tconsidered via the filters designed for severe accident conditions, such as to ensure a sufficiently long venting time”e• Prevents over-pressurization• Minimizes the radioactive releases into the environment and

decrease the off site dosesdecrease the off-site doses• Decreases the land contamination• H2 and other non-condensable gases concentration reduction

Containment Filtered VentingD i C id ti

Maintain Defense in Depth, the containment is the last Barrier

Design Considerationsp ,

(retention of aerosols inside containment) Aerosol retention better than 99.9%A l i b l th 0 5 iAerosol size may be lower than 0.5 micronsAbility to handle decay heatNo catastrophic failure scenarioNo catastrophic failure scenarioPassive actuation and operation Proven components with operating experienceMinimum impact on operation and maintenance of the plant “Install and Forget”No additional “concrete” for installationNo additional concrete for installationFlexible dimensioning for every possible locationMinimum weight for seismic qualificationg q

Sizing of the Filtered Venting SystemSizing of the Filtered Venting System5x105

Simulation of severe accidents

3x105

4x105

MP

a

on VVER-1000, V-320 ModelP and T in one different cavity geometries

1x105

2x105

P,

O C it

geometries• Containment design pressure = 5

bar

0 20 40 60 80

1x10

Time, h

One Cavity Two Cavities

600

• LB LOCA + Loss of all AC power supply sources

• Core Damage

500

550 • Vessel Failure + melt ejection• MCCI• Generation of steam and non

350

400

450 T, K • Generation of steam and non-

condensable gases • P and T increase

Diff t ti i f t t f th

0 20 40 60 80300

350

Time, h

One Cavity Two Cavities

• Different timing for startup of the filtered venting

Sizing of the Filtered Venting SystemSizing of the Filtered Venting System2,5x105

1 4 105

1,6x105

1,5x105

2,0x105

kg8 0 104

1,0x105

1,2x105

1,4x105

kg

5,0x104

1,0x105

Mas

s, k

2 0x104

4,0x104

6,0x104

8,0x104

Mas

s,

0 2 4 6 8 10-5,0x104

0,0 Cav 1 Cav 2

0 1 2 3 4-2,0x104

0,0

2,0x10

Melt ejected

• About 150 tons of melt transited to the cavity

Time, hTime, h

y• Steel door between the cavity and other containment

compartment (2nd cavity)Door failure and corium spreading• Door failure and corium spreading

Sizing of the Filtered Venting SystemSizing of the Filtered Venting System

5x105

520

4x105

5x10

a 440

460

480

500

K

2 105

3x105

P, M

Pa

VVER M 360

380

400

420

Tem

p,

VVER M

0 10 20 30 40 501x105

2x105 VVER M VVER L Limestone M Limestone L

0 10 20 30 40 50

320

340

360 VVER M VVER L Limestone M Limestone L

Comparison of P and T in VVER and Limestone concrete cases

Time, h Time, h

• Two cavities• Different structure of the molten pool

Mechanistic Mixture (available since MELCOR Version 1 8 3B)− Mechanistic Mixture (available since MELCOR Version 1.8.3B)− Stratified corium layers

Sizing of the Filtered Venting SystemSizing of the Filtered Venting System

Mass of Aerosols captured on filter

Total Decay Heat inside Containment

Decay Heat from Aerosols capturedAerosols captured on filter

Sizing of the Filtered Venting Systemg g y

P t WPNS Uk i B l iParameter WPNS (typical)

Ukraine Bulgaria

Start of venting, h 50.5 5.8 (37.2) 26.9

Temperature, ºC 223.3 138 (220) 139

Steam, % 53.3 70.1 66.2

H2, % 13.6 12.0 4.1

O2, % 4.8 3.7 4.9

Mass flow through the filter, kg/s 5.5 4.1 8.1

Mass median diameter, µm 1.44 / 0.95 1.48 / ---

Mass of filtered aerosols of theaerosols, kg

3.4 (229*) 11.0 (324*) --- (331*)

Residual heat on the filter, kW 8.1 (80*) 14.6 (---) --- (236*)Residual heat on the filter, kW 8.1 (80 ) 14.6 ( ) (236 )

* Total released radioactive substances (solid and gaseous)

Sizing of the Filtered Venting SystemSizing of the Filtered Venting System

The simulations produce substantially different resultsThe simulations produce substantially different results due to credible modifications of the starting conditionsMany of the phenomena are not yet well understood (limited experimental data)• Molten Core Concrete Interaction (including H2 generation)• Chemical reactions in and above the melt• Chemical reactions in and above the melt• Behavior of iodine (revolatilization in the sump, etc.)• Condensation and Settlement of aerosols on “heat surfaces”• Recombiners (air-mixing, iodine chemistry)

Limitations of the current code• One dimensional models are applied• One-dimensional models are applied• Nodalisation with gross transfers between nodes

Mitigation measures must be able toMitigation measures must be able to handle a wide range of condition

Design ConsiderationsA l Filt R i f i ti S l ti

Dry solution (German) relies on stainless steel filter mesh

Aerosol Filter – Review of existing Solutions

Dry solution (German) relies on stainless steel filter meshDry solution (France) relies on sintered steel filter cartridges downstream of the gravel bedsg gWet solution (Germany) relies on stainless steel filter mesh downstream of scrubber vesselWet solution (Switzerland) relies on “intelligent mixing” in scrubber vessel

Ultimate reliance on stainless steel filters is the pre-dominant solution

Implementation of Dry FiltersAerosol FiltersAerosol Filters

Concept proposal: 3 filter modules, each with 85 filter cartridges (1m length)Cartridge design is extremely flexible (length, diameter, arrangement) and will fit any footprint.Robustness of design provided by fully welded metallic cartridgesHEPA filter material: Sinterflo® F Metal Fibre

Design ConsiderationsSt i l St l filt Old & NStainless Steel filters – Old & New

Filter area each module:1.32m x 2.00m = 2.64 m2

Filter area each cartridge: 0.54 m2

(length of 1 m, outer diameter 60mm)Standard module w/ 8 surfaces8 x 2.64 m2 = 21.12 m2

Module: 6.21 x 1.42 x 2.7 = 23.8 m3

Proposed module w/ 85 cartridges85 x 0.54 m2 = 45.9 m2

(0.53m)2 x 3.14 x 1.43m = 1.26 m3

0.89 m2 filter / 1 m3 module volume( )36.4 m2 filter / 1 m3 module volume

Implementation of Dry FiltersAerosol FiltersAerosol Filters

HEPA filter material: Sinterflo® F Metal FibreUlt Hi h ffi i HEPA FiltUltra-High efficiency HEPA FilterHigh Permeability - Low Pressure LossPleated - Low Foot PrintDurability SS316 temperature resistant up to 340ºC

Efficiency of Sinterflo® 2F3 Metal Fibre

Durability SS316, temperature resistant up to 340 C

y

Design ConsiderationsSt i l St l filt B k dStainless Steel filters - Background

Design ConsiderationsR f M t i l C OH @ 60% idReference Material – CsOH @ 60% void

Densest packingofspheres 26% VOID

LiOH

SiO2

CsOH

CsI

UO2

Tolerance against void fraction uncertaintyCsOH(30%) = 22 mbar / CsOH(90%) = 3 mbarCsOH(30%) = 22 mbar / CsOH(90%) = 3 mbar

LiOH(30/90%) = 455/2 mbar – UO2(30/90%) = 8/1 mbar

Design ConsiderationsSt i l St l filt P ti l SiStainless Steel filters – Particle Size

R f P ti lReference Particle: 1 μm

13 mbar Δp- 13 mbar Δp

20 m2 filter will NOTNOT work if20 m filter will NOTNOT work if average particle smaller

than .54 μm

Design ConsiderationsSt i l St l filt L di (T l )Stainless Steel filters – Loading (Tolerance)

11 kg of CsOH11 kg of CsOHresult in

- 50 μm cakeμ- 13 mbar Δp

(@ 6200 m3/hr)

150 m2 filtration area providet t l i t bl kiextreme tolerance against blocking

Design ConsiderationsSt i l St l filt Filt ti S fStainless Steel filters – Filtration Surface

11 k f C OH11 kg of CsOH

150 m2 are in a flat almost linearflat almost linear

range of the variations.

Option: 2 systems to

increaseincrease robustness even

further

Surface Heatload Cake Δp20 m2 750 W/m2 374 μm 725 mbarμ

150 m2 100 W/m2 50 μm 13 mbar

300 m2 50 W/m2 25 μm 3 mbar

Implementation of New Dry Filters in V-320p y

Possible configuration - replacement of TL02 Aerosol Filtersg pEXISTINGAEROSOL  FILTERS

NewAEROSOL  FILTERS

Implementation of New Dry Filters in V 320Implementation of New Dry Filters in V-320Possible installation with the use of the existing penetrations TL42/TL22

A l filt i id t i t ( h f TL02 filt )Aerosol filters inside containment (exchange of TL02 filters) Iodine filters outside containment in A1022